This invention relates to a crawler belt suitable for use on crawler type vehicles such as hydraulic excavators, hydraulic cranes and the like.
Generally, crawler type vehicles such as hydraulic excavators are equipped with crawler belts for running or traveling purposes. Crawler belts of this sort are usually constituted by; right and left track links each having outer and inner link portions along opposite longitudinal sides thereof; bushes located transversely between inner link portions of the respective track links, and having transversely opposite ends of the respective bushes located in confronting relation with the outer link portions of the track links; connecting pins inserted in the respective bushes and having transversely opposite ends fitted and securely fixed in the outer link portions; and seal devices provided between the bushes and the outer link portions of the respective track links (e.g., as disclosed in Japanese Laid-Open Utility Model Publication No. S48-27535 and S49-113342).
The prior art crawler belts of this sort are each passed around an idle wheel and a drive wheel, and, as the drive wheel is rotated by a hydraulic motor or the like, the crawler belts are turned around between the idle and drive wheels to move a vehicle body in a forward or reverse direction.
Further, in the case of the prior art crawler belts just mentioned, rubber seals such as urethane rubber seals on the like are fitted between the bushes and outer link portions of track links to prevent intrusion of dirt or soil into gaps between the bushes and connecting pins, and at the same time to prevent leakage of grease which lubricates these members.
On the other hand, as another example of the prior art, there have been known crawler belts of a construction employing steel coned disc spring in place of the above-mentioned rubber seals for sealing gaps between the bushes and outer link portions of track links (e.g., as disclosed in Japanese Utility Model Publication No. S50-23945).
In the case of this prior art construction, as the crawler belts are turned around, the coned disc spring are held in sliding contact with end faces of the track links and bushes, thereby applying suitable sliding resistance to adjoining track links to prevent the crawler belts from flapping up and down to a considerably large degree.
Further, in another prior art crawler belt construction, ring-like spacers are fitted on connecting pins at positions between track links and bushes, and the spacers are each provided with a lip seal around its outer periphery for sliding contact with an end face of a bush; in association with a load ring which is adapted to press the lip seal resiliently toward the bush (e.g., as disclosed in Japanese Laid-Open Patent Publication No. H2-93170).
In the case of the prior art construction just mentioned, the thrust load which acts between the bushes and the track links is supported by means of spacers to prevent the thrust load from directly acting on the lip seals, thereby enhancing durability of the lip seals.
By the way, according to the prior art just mentioned, the rubber seals are interposed in a compressed state between the bushes and outer link portions of the track links and resiliently held in sliding contact with end faces of the bushes.
In this regard, in order to further enhance the sealing functions of the rubber seals, an increased 5 compressive load is applied to the rubber seals between the bushes and track links for the purpose of elevating the surface pressure of rubber seals which are in sliding contact with end faces of the bushes.
However, according to published prior art such as Japanese Laid-Open Utility Model Publication No. S48-827535, for example, if the compressive load on rubber seals is increased to an unnecessarily large degree, it will give rise to large sliding resistance between the rubber seals and bushes, causing abrasive wear to sealing surfaces of the rubber seals prematurely in an early stage and as a result deteriorating their sealing functions to a considerable degree.
Especially in case the compressive load is continuously applied to the resilient bodies of the rubber seals over a long period of time, plastic deformation (permanent deformation) could occur to the rubber seals due to fatigue. In such a case, the rubber seals are worn out between the bushes and gaps are opened depending upon the degree of wear to deteriorate their sealing functions.
Further, according to still another prior art construction as shown in Japanese Utility Model Publication No. S50-23945, seals of simple linear contact are formed by arranging coned disc springs in contact with outer link portions of the track links and end faces of the bushes. In this case, the contact areas of the coned disc springs and outer link portions are extremely small and insufficient to provide stable seals. In addition, coned disc springs are susceptible to corrosion or rust which would sooner or later lead to deteriorations in sealing functions.
Further, according to a prior art crawler belt construction as shown in Japanese Laid-Open Patent Publication No. H2-93170, load is applied to lip seals in a compressive direction by means of load rings of synthetic resin or similar resilient material. Naturally, the load rings of synthetic resin material as employed in this prior art are incapable of generating sufficient sliding resistance between the lip seals and bushes, thereby permitting the crawler belts to flap up and down easily during traveling operations to impair the performance quality of the machine in travel.
Furthermore, recently, it often become necessary for the crawler type vehicles of this sort to be moved from a remote working site to a nearby storage station or place which is located within a manageable distance. In such a case, since a transfer of a crawler type vehicle on a truck involves impractically troublesome steps, it has been the general practice to move a crawler type vehicle by itself for a travel to or from a working or storage place. Consequently, the crawler type vehicle is forced to travel over an unduly long distance, and, due to the large sliding resistance acting on the seals which are interposed between track links and bushes, the seals of the above-described prior art constructions lose sealing functions prematurely within a shortened period of time, thereby suffering from a short service life.
In view of the above-mentioned problems with the prior art, it is an object of the present invention to provide a crawler belt which uses seal rings in combination with coned disc springs in such a way as to enhance durability of the seal rings against loads acting in compressive directions, thereby ensuring a stable sealing capacity over a long period of time.
In order to achieve the objective just mentioned, according to the present invention, there is provided a crawler belt which includes right and left track links each consisting of a large number of track links successively connected in an endless form, each one of the track links being provided with an outer link portion at one longitudinal end and an inner link portion at the other longitudinal end thereof; bushes each located transversely between the inner link portions of the right and left track links to have opposite ends thereof in face to face relation with outer link portions of the truck links; connecting pins inserted in the bushes and having opposite ends thereof fitted in and connected to the outer link portions of the track links; and a sealing device located around a connecting pin in a gap spaces between an outer link portion of the track links and an opposing one of the bushes.
The crawler belt construction according to the present invention is characterized in that the sealing devices are each constituted by a seal ring formed of a resilient material in a ring-like shape having a diameter larger than that of the connecting pin and set in position to form a seal between the outer link portion and an opposing end face of the bush; and a coned disc spring interposed in a compressively deformable between the outer link portion and the bush and adapted to press the seal ring resiliently against the outer link portion and the end face of the bush.
With the arrangements just described, a transversely acting load (hereinafter referred to as xe2x80x9cthrust loadxe2x80x9d for brevity) which is imposed on the track links is supported by the coned disc spring of each sealing device between an outer link portion and a bush to suppress transmission of thrust load to the seal ring. Besides, by resilient force of the coned disc spring, the seal ring can be resiliently pressed against the outer link portion and an opposing end face of the bush to seal up the gap space between the outer link portion and the end face of the bush by surface contact.
In one preferred form of the present invention, the outer link portion is provided with a pin fitting hole to receive an end portion of the connecting pin, and a seal anchor hole formed coaxially with the pin fitting hole and adapted to hold the seal ring and coned disc spring of the sealing device between a bottom end surface thereof and the end face of the bush, abutting outer and inner peripheral ends, which are maximum and minimum in diameter, of the coned disc spring against the bottom end surface of the seal anchor hole and the end face of the bush, respectively.
With the arrangements just described, the coned disc spring can be located in a tapered shape converging toward the bush and in such a way as to press the seal ring strongly toward both of the outer link portion and the end face of the bush.
Further, according to the present invention, the end face as a whole of the bush can be constituted by a flat surface which is disposed normal to a longitudinal axis thereof. In this case, the end face of the bush can be machined easily as a perpendicular flat surface.
Alternatively, according to the present invention, the end face of the bush can be constituted by a seal ring abutting surface formed annularly in radially outer portions of the end face, and a circular coned disc spring abutting surface formed radially inward and projected axially outward of the seal ring abutting surface.
In this case, the gap space between the coned disc spring abutting surface and the outer link portion can be narrowed to an extent which corresponds to the length of axial projection of the coned disc spring abutting surface. Therefore, even in the case of a coned disc spring which has a smaller natural length in the transverse direction, it can be assembled into position between the outer link portion and the bush in a compressively deformed state. In addition, it becomes possible to make the gap space between the seal ring abutting surface and the outer link portion wider than the gap space between the coned disc spring abutting surface and the outer link portion for the purpose of securing a broader space from accommodating the seal ring.
Further, according to the present invention, both of the seal ring abutting surface and the coned disc spring abutting surface on the bush can be constituted by flat surfaces which are disposed normal to a longitudinal axis of the bush to provide an annular stepped portion therebetween.
In this case, the seal ring can be fitted on the annular stepped wall portion which is provided between the seal ring abutting surface and the coned disc spring abutting surface, thereby utilizing the stepped wall portion for setting the seal ring in position in the radial direction.
Further, according to the present invention, the seal ring abutting surface can be formed in a conical shape.
In this case, the seal ring abutting surface which is formed in a conical shape is disposed in an inclined state relative to the axis of the bush, so that it becomes possible to broaden the gap space between the coned disc spring and the seal ring abutting surface in proportion to the inclination angle of the latter.
On the other hand, according to the present invention, preferably, the coned disc spring is arranged to be capable of compressive deformation through a maximum flexural deformation distance L1 or L1xe2x80x2 which is in the relationship of (S1 less than L1 or S1 less than L1xe2x80x2) relative to a width S1 of the gap space between the outer and inner link portions of the track links.
With the arrangements just described, flexural deformation of the coned disc spring can be suppressed to a value smaller than its maximum flexural deformation distance L1 even when the inner and outer link portions are abutted (collided) against each other by a thrust load acting on the track links to make the gap space between the inner and outer link portions substantially to zero, thereby permitting the coned disc spring to retain excellent resilient force over an extended period of time. Accordingly, the coned disc spring can apply a pressing force on the seal ring to press the latter resiliently and continuously against the outer link portion and the end face of the bush.
Further, according to the present invention, preferably the coned disc spring is arranged to have an initial flexural deformation distance L2 or L2xe2x80x2 which is in the relationship of (L2 greater than S1 or L2xe2x80x2 greater than S1) relative to a width S1 of a gap space between the outer and inner link portions of the track links.
In this case, even when a thrust load is imposed on the track links to bring outer and inner link portions in one of right and left track links into abutting engagement with each other while spreading apart the gap space between outer and inner link portions in the other track link to a width approximately two times as large as the gap width S1 (2xc3x97S1), the coned disc spring can be retained in a resiliently deformed state between the outer and inner link portions. Accordingly, the coned disc spring can press the seal ring resiliently and continuously against the outer link portion and the end face of the bush by applying a resilient force on the seal ring in a stabilized manner.
Further, according to the present invention, preferably the seal ring and the coned disc spring are arranged to have jointly an initial flexural deformation distance P or Pxe2x80x2 which is larger than a width S1 of a gap space between the outer and inner link portions of the track links and set in the relationship of (P greater than S1 or Pxe2x80x2 greater than S1)
In this case, similarly the coned disc spring can be retained in a resiliently deformable state between the outer and inner link portion even when the gap space between the outer and inner link portions is spread apart to a width approximately two times as large as the gap width S1 (2xc3x97S1) by a thrust load acting on the track links. Accordingly, the coned disc spring can apply a resilient force to the seal ring continuously in a stabilized manner.
Further, according to the present invention, preferably the coned disc spring is set between the connecting pin and the seal anchor hole, having an outer peripheral end portion thereof spaced from the seal anchor hole in radial direction by a gap of width S2 or S2xe2x80x2 which is smaller than a radial gap space S3 or S3xe2x80x2 between an inner peripheral end portion of the coned disc spring and the connecting pin, i.e., in the relationship of (S2 less than S3 or S2xe2x80x2 less than S3xe2x80x2).
With the arrangements just described, the inner peripheral end portion of the coned disc spring can be retained out of contact with the connecting pin, so that the coned disc spring is prevented from getting into sliding contact with circumferential surfaces of the connecting pin even if the coned disc spring is caused to rotate along with the bush while the track link is being turned around.
Further, according to the present invention, the seal ring and the coned disc spring may be formed separately of each other and set in position in an assembled state between the outer link portion and the end face of the bush. Therefore, at the time of parts replacement of the sealing devices, the seal rings and coned disc springs can be replaced individually and independently of each other.
Furthermore, according to the present invention, the seal ring and the coned disc spring may be formed into and provided as one integral structure. At assembling for the sealing device, the assembling work for the seal ring and coned disc spring separately into the seal anchor hole can be facilitated to a significant degree.